Computer Graphics Introduction

1. Computer GraphicsIntroduction

2. Graphics: All aspects of the production of pictures (images) using a computer Application areas: Display of Information Design Simulation User Interfaces

3. Basic Graphics System: Processor Memory Frame buffer Output device Input device Basic Graphics System: Processor Memory Frame buffer Output device Input device Basic Graphics System: Processor Memory Frame buffer Output device Input device Basic Graphics System: Processor Memory Frame buffer Output device Input device Basic Graphics System: Processor Memory Frame buffer Output device Input device Basic Graphics System: Processor Memory Frame buffer Output device Input device

4. Pixels & Frame buffer Raster: array of pixels Pixel: picture element Frame Buffer: memory area used to store pixel/raster data VRAM: Video random access memory DRAM: Dynamic random access memory Depth: number of bits of information stored for each pixel Resolution: number of pixels in frame buffer (on screen)

5. Processor: - may be main CPU or special purpose processor on video card - performs Rasterization (Scan Conversion) conversion of geometric primitives (line, circle, etc) to pixel values in frame buffer

6. Output devices CRT: Cathode Ray Tube refresh flicker triads shadow mask CRT: Cathode Ray Tube refresh flicker triads shadow mask LCD: Liquid crystal display

7. RASTER SCAN Refresh

8. Output devices CRT: Cathode Ray Tube refresh flicker triads shadow mask

9. SHADOW MASK TRIAD

10. Vector Displays graphics primitives are made of sequences of strokes or vectors Raster Displays display graphics primitives in a refresh buffer in terms of the primitive’s component pixels

11. Vector Displays graphics primitives are made of sequences of strokes or vectors IDEAL LINE DRAWING RANDOM SCAN

12. Raster Displays display graphics primitives in a refresh buffer in terms of the primitive’s component pixels IDEAL LINE DRAWING RASTER SCAN

13. Raster Displays display graphics primitives in a refresh buffer in terms of the primitive’s component pixels IDEAL LINE DRAWING FILLED RASTER SCAN

14. IMAGES: Point: a location on an object (or in space) relative to a Reference Coordinate System Cartesian Coordinates: 3D space, perpendicular axes, equal distance measures on each axis Object: specified by an organized grouping of Metric and topological information Vertices: corner points. They carry metric information -- (X,Y,Z) coordinates. Vertex listing: list of vertex identifiers forming polygon boundary (usually a list of indices into the vertex array)

15. Image creation: NOTE: An image is generally a 2D projection or rendering of a 3D scene What must be specified (known) 1 - What are the objects in the scene 2 - Where are the objects in the scene 3 - Where is the viewer 4 - Where is the viewer looking 5 - What type of projection is assumed 6 - Where are the lights 7 - .... 1 - What are the objects in the scene 2 - Where are the objects in the scene 3 - Where is the viewer 4 - Where is the viewer looking 5 - What type of projection is assumed 6 - Where are the lights

16. Light: visible part of the electromagnetic spectrum Wavelength: identifies light color (350-780 nanometers) Light sources characterized by location, nature (point or area), color, brightness (Simplifying assumption for now -- assume monochromatic (single color) lights)

17. Ray tracing is a method for following the path of a photon from its origin at a light source, bouncing off the various surfaces it strikes, before it strikes the image plane.

19. Film Pinhole The Pinhole Camera Simple model for a camera. The pinhole allows only a small number of light rays to pass through from the scene to the film.

20. Eye Computer graphics model of pinhole camera The pinhole is replaced by the eye and the film plane moves out in front of the pinhole (eye).